In this work I will present our latest advances in components developed from extraordinary transmission concepts operating at terahertz (THz) frequencies. First, a structure exhibiting two different extraordinary transmission resonances depending on the polarization of the incident wave will be shown. The peaks of transmission appear at approximately 2 and 2.5 THz for vertical and horizontal polarization, respectively, with a transmittance above 60% in both cases. Later on, a meandering line structure able to tune the extraordinary transmission resonance will be discussed. The operation frequency in this case is between 9 and 17 THz. A self-complementary polarizer will be then presented, with a high polarization purity. The fundamentals of this device based on the Babinet’s principle will be discussed in depth. Finally, all these structures will be combined together to produce a dual-band Quarter Wave Plate able to convert a linear polarization at the input in a circular polarization at the output at two different bands, 1 and 2.2. THz. Some final words regarding the potential of extraordinary transmission for sensing applications will close the contribution.
The progress in developing metallic metamaterial lenses founded on stacked subwavelength hole arrays is reported.
Before, the lens was studied when it emulates a medium with effective index of refraction -1. Here, the lens is
investigated at higher frequencies, where it behaves like a near-zero index of refraction. We show that exploiting both
regimes, dual-band capabilities are attainable. Moreover, a zoning technique is applied to the initial design to reduce the
lens in terms of volume and weight, while the performance is maintained.
Novel antennas exhibiting directivity enhancement by using a short focal length plano-concave lens engineered by
stacked subwavelength hole arrays in such a way that an effective negative index of refraction is obtained. An additional
unexpected property of this design is that it opens the possibility to achieve an index close to zero, n → 0, arisen from ε-
and μ-near-zero extreme values. Our original design works with evanescent modes in comparison with the well known
classical metallic lenses operating with propagating modes. In our case, this leads to a negative index of refraction,
whereas metallic lenses exhibit a positive but less than one index of refraction. It is demonstrated by means of a simple
design based on dispersion diagram and ray tracing an easy and correct method for rather accurate results. Also, an
optimization of the hole diameter or longitudinal lattice constant to achieve not only n = -1, but also free space matching
is possible simultaneously. A power enhancement up to 24 dB with cross-polarization below -30 dB with regards to co-polar,
when the lens is applied as antenna radiation beamforming has been measured. For the case of index close to zero,
n → 0, the power enhancement is 27 dB whereas the cross-polarization remains -17 dB with regards to co-polar. New
improvements are under analysis in order to determine if this technology could be competitive with current state of the
art of waveguide lenses and Fresnel zone plate lenses.
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